GENEVA — Glaciers in Antarctica are melting faster and across a much wider area than previously thought, a development that threatens to raise sea levels worldwide and force millions of people to flee low-lying areas, scientists said Wednesday.

Researchers once believed that the melting was limited to the Antarctic Peninsula, a narrow tongue of land pointing toward South America. But satellite data and automated weather stations indicate it is more widespread.

The melting "also extends all the way down to what is called west Antarctica," said Colin Summerhayes, executive director of the Britain-based Scientific Committee on Antarctic Research.

"That's unusual and unexpected," he said.

By the end of the century, the accelerated melting could cause sea levels to climb by 3 to 5 feet — levels substantially higher than predicted just two years ago.

The report Wednesday from Geneva was a broad summary of two years of research by scientists from 60 countries. Some of the findings were released in earlier reports.

In Washington, as part of an overall update on global warming, top researchers on Wednesday sounded a similar warning to the U.S. Senate about rising temperatures in the Antarctic.

The head of the Intergovernmental Panel on Climate Change, set up by the United Nations, told lawmakers on the Environment and Public Works Committee that Earth has about six more years at current rates of carbon dioxide pollution before it is locked into a future of severe global warming.